1. Field of the Invention
This invention relates to adaptive control systems, and particularly to a system in which the change in position of a controlled device in response to a discrete control pulse is measured, and the duration of the next occurring discrete control pulse is varied in response thereto. The invention has the advantage of reducing the cost and complexity of the servo actuating system for the controlled device.
2. Description of the Prior Art
Control systems such as servomechanisms for regulating the position of a controlled device in response to a control signal are well known in the art. In the aircraft industry, for example, it is desired to accurately control the position of the rudder, elevator, flaps and other components in response to pilot initiated or automatic control system inputs. Various components of turbine engines such as fuel control valves, exhaust nozzle actuators and variable geometry vanes are also positioned in response to control signals generated by control systems.
In the past it has been necessary, in order to assure that the controlled device is moved in a sufficiently fast yet stable manner to a desired position, to incorporate complex servo systems such as torque motors and hydromechanical servo amplifiers in the mechanical portion of the control system. These hydromechanical servos used internal feedback devices to provide fast yet stable operation and were constricted to close mechanical tolerances. Even with the advent of electronic control systems, similar expensive and complex mechanical systems were used to respond to the electronic control signals and to regulate the position of the movable mechanical element.
Although considerable progress has been made in lowering the cost and increasing the capabilities of electronic control systems by utilizing digital computation techniques and integrated circuit technology, this progress has been made by advancing the technology of the electronic control unit itself rather than the associated mechanical units which respond to the electronic signals and control the position of the movable controlled device. In all cases, the outputs from the electronic portion of the control systems are required to operate through mechanical or hydraulic systems in order to drive the controlled device. As control systems become more complex, more of the mechanical components are required, and in terms of cost, size and weight the mechanical portions of the system have become the most significant in the overall control system.
This situation is further aggravated by the fact that little advance has been made in servomechanical system technology to utilize the logic capabilities of the electronic controls, many of which contain digital computers therein. In fact, the servomechanical systems used in today's controls are essentially the same as those used with relatively unsophisticated analog electronic systems of many years ago. In many of today's electronic engine controls used on aircraft, the cost of the electronics is only one fourth of the total cost of the entire control system.
The present invention is directed to a novel adaptive control system which makes full use of the capabilities of an electronic control computer to reduce the cost, complexity and accuracy requirements of the servomechanical portion of the system, resulting in a low cost yet rapid acting control system having infinite resolution, and which operates from a discrete switched input control signal to the servomechanical portion of the system. As a consequence, the tolerances and restraints on the cost and design of the servomechanical portion of the system are considerably reduced since no complex or expensive feedback is required in the servomechanical system to assure that the controlled device, a movable mechanical element subjected to wide load variations, is properly positioned in response to the electronic control signal. By reducing the cost and weight of the servomechanical portion of the system at the expense of a slight increase in complexity of the electronic portion of the system, the total cost and complexity of the entire control system is considerably reduced.